Djokovic is Serbian, this involves added layers of unconditional non-ironic love for your country inhabitants of select few countries can produce these days. Djokovic's "national hero" status is different to Federer's "national hero" status in Switzerland too.
"the Olmypics are mainly for your country" as a recent cliche - are we talking about Olympics in general or tennis at Olympics?
What I mean by this is that as much as Federer is loved in his country, he transcended it, he's "international", an icon, the world's property now.
Djokovic is still much more "country-bound", and that is a country with a rich recent history, Djokovic represents Serbia all over the world and he sort of carries loads of national pride on his shoulders. He simply HAS TO do it at this tournament not only for himself, but much more for the people of Serbia.